Sewing machine

ABSTRACT

A sewing machine including a means for imparting tension to a drawn out thread by driving it rotatively in a direction opposite to that in which said thread is being drawn out, is provided with means for preventing said drawn out thread from being retrogressed comprising a movably mounted pressing member and a fixed member which normally let said thread pass through said retrogression preventing means but stationarily hold the thread if and when the drawn out tension of said thread is lost, for instance when the thread breaks at a point downstream from the retrogression preventing means.

United States Patent 1191 Matsumoto Dec. 31, -1 974 SEWING MACHINE 3,081,014 3/1963 Anderson et a1; 226/147 [75] Inventor: Mitsuo Matsumoto, Tokyo, Japan FOREIGN PATENTS OR APPLICATIONS 73 Assignee; Nara Sewing Machine Industrial 915,719 1/1963 Great Britain 112/254 7 Co Ltd" Tokyo, Japan 2,031,006 3/1971 Germany 242/150 M I 1 [22] Filed: 1973 Primary Examiner-George H. Krizmanich [211 App] 342,246 Attorney, Agent, or Firnr-Cushman, Darby &

v Cushman [30] Foreign Application Priority Data [57] ABSTRACT June 7, 1972 Japan 47-056050 A sewing -machi'ne including a means for imparting 52 U.S. c1 112/255 226/151 226/153 tension draw" thread by driving it rmatively 526/155 242/l55 in a direction opposite to that in which said thread is 1511 Int. Cl 1)0Sb 47/04 being drawn is provided with means for prevent 58 Field of Search 112/254, 255;-242/155 R, mg E draw thread from belng retrofresseg 242/150 M; 226/151, 153 154 155 147 40 comprislng a movably mounted pressing mem er an a fixed member wh1ch normally let said thread pass through said retrogresslon preventing means but sta- [56] References Cited tionarily hold the thread if and when the drawn out tension of said thread is lost, for instance when the UNITED STATES PATENTS thread breaks at a point downstream from the retro- ROSC gression preventing means 2,389,834 11/1945 Wyrick 226/40 X 3,058,64l 10/1962 Peterson 226/153 X 4 Claims, 6 Drawing Figures PATENTEDBEBS 1 1914 857' 347 sum 3 or 5 FIG.4

SEWING MACHINE CROSS REFERENCE TO RELATED APPLICATION The present invention is an improvement upon the invention disclosed in my copending United States patent application, Ser. No. 213,080, filed Dec. 28, 1971, now US. Pat. No. 3,786,771, issued .Ian. 22, 1974.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sewing machine comprising a means for imparting tension to a drawn out thread for letting said thread float, and a means for preventing said drawn out thread from being inversely moved.

2. Description of the Prior Art In the prior art of this field there have been many sewing machines provided with means for imparting tension .to the drawn out threads of sewing machines.

For example, one of the samples of those of the means for imparting tension to the 'drawn out threads of the sewing machine of the prior art is shown in FIG. 1. 1

In the prior art almost every means for imparting tension to the drawn out threads of the machines are arranged as follows: that is, typically each of them comprises an eccentric cam, a driving shaft, an operating member, a coupling, a rod, a spring and a dish-shaped plate for holding the drawn out thread. The arrangement and operation of the means for imparting tension to the drawn out thread are such as described in detail hereinafter.

Shown as in FIG. 1, the eccentric cam 103 is fitted up to the driving shaft 6 which is mounted rotatably on the body of the sewing machine, and the operating member 104 is cooperated with the surface of this cam, and the rod-I06 is coupled with the operating member 104 through the coupling 105. On the upper end of the rod 106 the dish-shaped discs 108 composed of two plates, one of them being placed on the other, and both of them being pressed by the spring 107 is fitted, whereby the holding and releasing operations for the drawn out thread of the sewing machine are achieved.

Accordingly, with these operations the operating member 104 is actuated to make up and down movements by the eccentric cam 103 rotated by the driving shaft 6, and at the same time the rod 106 is also actuated to make the same movement, up and down movements, through the coupling 105. As the result of those operations the holding discs 108 are given opposite movements, whereby the thread at one case is given tension when it passes through between the discs, and then it is released when it passes through between the discs in the interlocking motion cycle of the sewing machine.

However, it is impossible for such a mechanism as described above to achieve precise motion in interlocking relation; that is, the operating member can not be followed to the surface of the eccentric cam in case when the driving shaft is rotated with high speed, and as a result of the aforementioned it occurs that the holding discs do not make the up and down movements at extremely high speed working. Accordingly, the released means of the sewing machine; and

condition of the thread continuously occurs which causes an intermittent sewing operation, butalso prevents the sewing machine from having a capability of high speed acceptible sewing. Further, the sewing machine of the prior art mentioned above also has the disadvantages of being noisy and needing to be lubricated frequently.

Moreover, it also the disadvantage that when the drawn out thread is suddenly cut in working, the cut thread entangles with the rollers of the means for imparting tension to the thread.

Therefore, in view of the foregoing the necessity of providing a means for preventing the drawn out thread from retrogressing movement, Le, a reversal prevention means became apparent.

SUMMARY OF THE INVENTION tension and releasing tension to the thread precisely so as to be able to permit high speed sewing work in the sewing machine.

The third object of the present invention is to give a sewing machine provided with a means for imparting tension to the drawn out thread thereby preventing the sewing machine from being noisy in sewing work and from needing frequent lubrication.

The fourth object of the present invention is to give a sewing machine provided with a means for preventing the drawn out thread from reversive movement, i.e., a reversal prevention means for the purpose of preventing the thread from entangling with rollers of a means for imparting tension to the drawn out thread in case of the thread being cut in working.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic sectional front elevation of a part of the sewing machine of the prior art;

FIGS. 2 to 5 show an embodiment of the present :invention, wherein FIG. 2 is a perspective view of a sewing machine provided with an embodiment of the present invention,

FIG. 3 is a top plan view of the main portion of the present invention,

FIG. 4 is a partially cut-away-side elevation of a means for imparting tension to the drawn out thread of the sewing machine of the present invention,

FIG. 5-I and FIG. 5-II illustrate two successive steps in the working operation of the tension imparting FIG. 6 is a partially cut-away side elevation view of a means provided in accordance with the present invention for preventing the thread from its reverse movement.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The present invention is an improvement upon the invention disclosed in my copending United States patent application, Ser. No. 213,080, filed Dec. 28, 1971, now US. Pat. No. 3,786,771, issued Jan. 22, 1974.

At first referring to the accompanying drawings the present invention is illustrated in detail with respect to the preferred embodiment.

FIG. 2 is a schematic view of a whole sewing machine which provided with a means for imparting tension to the drawn out thread and a means for preventing the thread from being retrogressed. (A) is a means for imparting tension to the thread and (B) is a reversal prevention means, i.e., the means for preventing'the thread from being retrogressedAs shown in FIG. 2, both means are mounted on the body 1 of the sewing machine, and (B) is positioned downstream from (A).

In HS. 3 and FIG. 4 it is shown that the means for imparting tension to the thread, (A), includes a roller 4 on a rotating shaft 2 pivotallyfixed to the body 1. The roller 4 has a flat channel 3 on a part of the outer surface thereof. The roller 4 rotates in-a direction which moves its'outer peripheral surface in opposition to the advancing thread. At the lower end of the rotating shaft 2 a bevel gear 5 is mounted and it is engaged with a bevel gear 7 mounted on the-driving shaft 6.

The driving shaft 6 is arranged so as to be interrelatingly operated with a means for drawing out the thread (not shown). The driving shaft 6 is also adapted to rotate one rotation'as the roller 4, makes one precise rotation. Y

A pressing lever 9 is mounted ,rotatably on the body of the sewing machine through a supporting axis 8 and has a pressing surface 10 which is adapted to be alwaysin contacting relation with the roller 4, so as to let a crossed portion 11 at the other end of the pressing lever 9 loosely engage with a guide rod 12 mounted on the body of the sewing machine and at the same time the pressing surface '10 is energized so as to be always pressed into contact with the surface'of the roller by a coil spring 13.

Next, the arrangement and'operations of'the reversal prevention means (B) of the thread are described.

As shown in FIG. 3 and P10. 6 an axial pin-shaped fixed member 14 is mounted on the body 1 by being inserted therein, and a movable member 15 (which is resiliently disposed against the fixing member 14) is'pivotably supported on the body 1. The top surface 15 of the movable member 15 is adapted to always contact the fixing member 14 due to the resilience of the spring 17. In the drawings (a) is the drawn out thread of the sewing machine.

As described above, according to the present invention the means for imparting tension to the thread a rol- I the pressing lever 9, and is thereby tensional. When the ler 4 provided with a channel for releasing the thread channel-like shaped portion of the roller coincides with the pressing lever the thread is released as shown in H6. S-ll.

If the thread which is being drawn out sequentially by the particular arrangement and operation above mentioned is suddenly cut'during the sewing operation, sometimes, were it not for provision of the apparatus of the present invention, the thread between thetension imparting means (A) and the needle not shown, may retrogress causing the thread to become entangled with the roller 4 of the tension imparting means.

This is prevented by providing a means (B) for preventing the thread from retrogressing movement, and that operation of the means is as follows.

The thread (a) is moved with appropriate tension provided at (A) in the direction indicated by arrow head on the thread (a). In this case the pressing force between the roller 4 and the pressing member 9 against the thread is slightly smaller than the pressing force against the thread between the fixing member 14 and the movable member 15. Immediately, when the thread is suddenly cut and the tension of the thread is lost, the top end 15' of the movable member 15 is tightly pressed against the fixed member 14 by the resilience of the spring l7, preventing retrogressive movement of the thread and the thread is caught in a manner like a worm being bitten by a bird. I

As may be clearly understood from FIG. 3, it is-the part of the thread which has passed through the movable member 15 that would cause hindrances incase of the thread being out were the apparatus (B) not provided.

Since the pressing force against the thread of the movable member 15 gives scarcely any effects both to the cloth and the thread, it is necessary that the arrangement of the present invention must be adapted such that the pressing provided at l4, 15 is always slightly larger than that provided between the roller 4 and the pressing lever 9 of the means (A).

Of course, it should be evident that the thread slips through at both 4, 9 and l4, 15' during normal sewing operations, for forward-pulling the tension of the thread at the needle is considerably larger during ordinary sewing than the drag at 14, 15' and 4, 9.

As mentioned heretofore, according to the present invention, both the means for imparting tension to the thread and the means for preventing the thread from retrogressing are necessary for making the sewing work of the sewing machine precisely and speedily, and the important feature of the present invention lies in providing both means in the sewing machine so as to interrelate these functions appropriately whereby smooth and precise sewing work being expected.

It will be understood that the above described armeans journalling the .roller, said body and rotating the roller opposite to the direction of the thread being fed;

means defining a generally tangentially proceeding notch in the radially outer periphery of the roller, said notch being of less than circumferential extent, the radial extent of the roller thus being greater angularly beyond the notch than within the notch;

a generally L-shape thread urging member having means defining a convex arcuate surface on one leg thereof;

pin means pivotally mounting the thread urging member on the body, and

means resiliently biasing the thread urging member about the pin means in a sense to bias the convex arcuate surface of the thread urging member into resilient contact with the radially outer periphery of the roller;

the shape and extent of the convex arcuate surface relative to the shape and extent of the radially outer periphery of the roller being such that the convex arcuate surface fails to fully obstruct the notch and defines a gap that is open from one angular extreme of the notch to the other when the notch is presented toward the convex arcuate surface, said gap being sufficient in thickness to permit the thread being fed between the roller and the convex arcuate surface to slip forwards when the notch is presented toward the convex arcuate surface; and

a thread retrogression preventing means comprising:

fixed pin means mounted on said body;

a movable member mounted on said body; resilient means biasing the movable member into resilient engagement with the fixed pin;

the thread retrogression preventing means being interposed in the path of the thread downstream.

from the tension imparting means, and positioned to resiliently engage and pass the thread between the fixed pin means and the movable member,

the resiliency provided by the resiient biasing means associated with the movable member being sufficiently strong compared to the resiliency provided by the resilient biasing means associated with the thread urging member, that should the thread become severed downstream from the thread retrogression preventing means during sewing, the latter will prevent the tension imparting means from pulling the thread back upstream through the thread retrogression preventing means and into entanglement with said roller.

2. The apparatus of claim 1 wherein the resilient biasing means comprises:

means defining an opening through the other leg of said thread urging member; an L-shaped rod having one leg mounted on the body 5 and having the other leg loosely extending through said opening; threading on said other leg of the rod outwardly beyond said opening; nut means threaded on said threading; and a compression coil spring about said other leg of the rod urging betweenrthe nut means and the other leg of the rod.

3. The apparatus of claim 1 wherein the notch is shorter, axially of the roller, than said convex arcuate surface to prevent that surface from entering the notch.

4. In a sewing machine wherein the action of stitching pulls thread along a path from a supply:

a sewing machine body; means on thebody for imparting tension to the thread being fed, comprising first and second members resiliently squeezing the thread between them at a point on said path between the supply and where stitching takes place, and means for rotating one of said members in a sense to tend to withdraw the thread upstream toward the supply with a lesser force than the force with which the pulling action of the stitching tends to draw the thread downstream, whereby the thread is placed between the tension imparting means and where stitching takes place; the tension imparting means including relief means for cyclically, intermittantly substantially reducing and increasing the force with which the tension imparting means resiliently squeezes the thread, in order to cyclically intermittantly increase and decrease the rate of feeding of the thread; and a thread retrogression preventing means comprising:

means resiliently squeezing the thread at a point on said path between the tension imparting means and preventing means.

upstream, that should the thread become severed 

1. In a sewing machine: a sewing machine body; means for imparting tension to a thread being fed comprising: a roller; means journalling the roller said body and rotating the roller opposite to the direction of the thread being fed; means defining a generally tangentially proceeding notch in the radially outer periphery of the roller, said notch being of less than circumferential extent, the radial extent of the roller thus being greater angularly beyond the notch than within the notch; a generally L-shape thread urging member having means defining a convex arcuate surface on one leg thereof; pin means pivotally mounting the thread urging member on the body, and means resiliently biasing the thread urging member about the pin means in a sense to bias the convex arcuate surface of the thread urging member into resilient contact with the radially outer periphery of the roller; the shape and extent of the convex arcuate surface relative to the shape and extent of the radially outer periphery of the roller being such that the convex arcuate surface fails to fully obstruct the notch and defines a gap that is open from one angular extreme of the notch to the other when the notch is presented toward the convex arcuate surface, said gap being sufficient in thickness to permit the thread being fed between the roller and the convex arcuate surface to slip forwards when the notch is presented toward the convex arcuate surface; and a thread retrogression preventing means comprising: fixed pin means mounted on said body; a movable member mounted on said body; resilient means biasing the movable member into resilient engagement with the fixed pin; the thread retrogression preventing means being interposed in the path of the thread downstream from the tension imparting means, and positioned to resiliently engage and pass the thread between the fixed pin means and the movable member, the resiliency provided by the resiient biasing means associated with the movable member being sufficiently strong compared to the resiliency provided by the resilient biasing means associated with the thread urging member, that should the thread become severed downstream from the thread retrogression preventing means during sewing, the latter will prevent the tension imparting means from pulling the thread back upstream through the thread retrogression preventing means and into entanglement with said roller.
 2. The apparatus of claim 1 wherein the resilient biasing meaNs comprises: means defining an opening through the other leg of said thread urging member; an L-shaped rod having one leg mounted on the body and having the other leg loosely extending through said opening; threading on said other leg of the rod outwardly beyond said opening; nut means threaded on said threading; and a compression coil spring about said other leg of the rod urging between the nut means and the other leg of the rod.
 3. The apparatus of claim 1 wherein the notch is shorter, axially of the roller, than said convex arcuate surface to prevent that surface from entering the notch.
 4. In a sewing machine wherein the action of stitching pulls thread along a path from a supply: a sewing machine body; means on the body for imparting tension to the thread being fed, comprising first and second members resiliently squeezing the thread between them at a point on said path between the supply and where stitching takes place, and means for rotating one of said members in a sense to tend to withdraw the thread upstream toward the supply with a lesser force than the force with which the pulling action of the stitching tends to draw the thread downstream, whereby the thread is placed between the tension imparting means and where stitching takes place; the tension imparting means including relief means for cyclically, intermittantly substantially reducing and increasing the force with which the tension imparting means resiliently squeezes the thread, in order to cyclically intermittantly increase and decrease the rate of feeding of the thread; and a thread retrogression preventing means comprising: means resiliently squeezing the thread at a point on said path between the tension imparting means and where stitching takes place, with sufficiently greater force compared to that with which the tension imparting means tends to withdraw the thread upstream, that should the thread become severed downstream from the thread retrogression preventing means during sewing, the latter will prevent the tension imparting means from pulling the thread lack upstream through the thread retrogression preventing means. 